The treatment of gaseous streams for removal of acid gases, such as hydrogen sulfide and carbon dioxide, is an essential processing step in petroleum refining, natural gas production, and the petrochemical industry. Myriad technologies have achieved commercial status, each satisfying for a particular set of circumstances a required balance among operability, process requirements, flexibility, and economic factors.
Such processes include the use of physical solvents, aqueous solutions of chemical agents (amines, carbonates, redox systems), solvent/chemical mixtures, and solid adsorbents, etc.
Historically, gas treating problems have been of three main types - hydrogen sulfide removal, the simultaneous removal of hydrogen sulfide and carbon dioxide, and carbon dioxide removal with little or no hydrogen sulfide present. The present invention pertains to the removal of acid gases, particularly to carbon dioxide, from gaseous streams containing little or no sulfur gases, such as in gaseous streams used in the manufacture of hydrogen and ammonia.
One leading type of process for the removal of CO.sub.2 from gaseous streams which has met with commercial success is the so-called "hot pot" process. The hot pot process is based on the use of a hot aqueous potassium carbonate solution to convert the CO.sub.2 to potassium bicarbonate. An activator, or promoter, is usually used to improve the absorption rate and/or capacity of the solution and a V.sup.+5 salt is often used as a corrosion inhibitor. Non-limiting examples of promoters used in the hot pot process include alkanolamines, particularly diethanolamine (DEA), sterically hindered polyamines, such as N-cyclohexyl-1,3-propanediamine (CHPD) and sterically hindered amino acids such as N-secondary butyl glycine (SBG). While all of these promoters have met with varying degrees of commercial success, they are all faced with shortcomings. For example, DEA has a relatively low absorption rate and capacity and is not very stable. CHPD requires a cosolvent and undergoes degradative reactions, and SBG undergoes oxidative degradation in the presence of vanadium.
Consequently, there exists a need in the art for promoters for hot pot processes which not only have relatively high absorption rates and working capacities, but which are not susceptible to degradation under process conditions or in the presence of vanadate corrosion inhibitors.